1. Field of the Invention
This invention relates to an ethylene-.alpha.-olefin vulcanized rubber composition having a high strength and further an excellent thermal resistance, excellent weather resistance, and high transparency.
Uses of rubber compositions which require a high strength, thermal resistance and weather resistance and further a high transparency include automotive parts, industrial goods, electrical parts, etc. Rubber compositions having such properties can be used, for example, as materials for tubes, hoses, sheets, rolls, and the see-through part of masks and the like. Further, they can be used to form composite materials by combining them with glass or transparent resins such as polymethyl methacrylate and polycarbonate.
2. Description of the Prior Art
It is known that rubber composition with some transparency, called "semi-translucent rubber", can be obtained by adding to ethylene-.alpha.-olefin rubber silica and/or magnesium carbonate as a reinforcing filler. However, they have defects of a low total light transmittance and a high haze value.
The present inventors have already obtained vulcanized rubber compositions which give a high total light transmittance and a low haze value by vulcanizing with an organic peroxide an unvulcanized rubber composition characterized by being formed by adding to an ethylene-.alpha.-olefin rubber 10 to 70 parts by weight of anhydrous silica with an average particle diameter of its primary particles of 20 nm or less relative to 100 parts by weight of said rubber without addition of metal oxides or metal carbonates thereto (see Japanese Patent Application No. 183,753/85).
However, these rubber compositions are still of low strength and unsatisfactory in thermal resistance, weather resistance, etc. because they contain no metal oxide nor metal carbonate added thereto. Accordingly, improvement thereof has been eagerly awaited.